The research plan outlined here could disclose a number of applications for electrodes chemically modified with electroactive coatings in the neurophysiology area, including new methods for microiontophoresis, monitoring neurotransmitter release, and transduction of nerve signals. The iontophoretic method would control the ionic content of the coating (and the surrounding solution) by controlling the oxidation state of the redox centers in the coating. Selective removal as well as injection of certain ions will be described. Another new possiblity is the simultaneous application of ionic stimuli to selected areas and complicated geometries of physiological interest. A separate potential application for chemically modified electrodes is the in vivo detection of neurotransmitter release by voltammetric methods. Interactions of neurotransmitters with chemically modified electrodes will be investigated in this task to determine the feasibility of using such electrodes for in vivo determination of nonelectroactive as well as electroactive transmitters. The effects of transmitters on the rate of electron transfer between the immobilized species and another redox species in solution will be determined. These results will be correlated with electrical measurements that may be applied in vivo. It should be possible to tailor the neighborhood of an electroactive site to resemble that of a neural receptor site. Another possible outgrowth of this research is production of improved electrodes for neural stimulation.